LHC Collimation and Loss Locations

Transcription

1 BLM Audit p. 1/22 LHC Collimation and Loss Locations BLM Audit Th. Weiler, R. Assmann, C. Bracco, V. Previtali, S Redaelli Accelerator and Beam Department, CERN

2 BLM Audit p. 2/22 Outline Introduction / Motivation LHC Layout The LHC Challenge Collimation Principle / Multi Stage Cleaning Loss Rates Intensity and Cleaning Inefficiency Simulations: SixTrack and Beam Loss Pattern Loss location around the ring (injection and top energy) Summary

3 BLM Audit p. 3/22 Layout of the LHC Ring C. Bracco 7 TeV protons for collision super-conduction magnets to bend and focus beam four experimental insertions two dedicated cleaning insertions in region with normal conducting magnets dump protection (in case of kicker failure)

4 BLM Audit p. 4/22 The LHC Challenge R. Assmann Stored beam energy 360 MJ, 200 times larger than any other existing proton machine, enough energy to melt 500 kg of copper. For quenching a superconducting magnet one needs mj cm 3

5 BLM Audit p. 5/22 Multi-Stage Cleaning CFC CFC Cu / W tertiary collimator: W

6 BLM Audit p. 5/22 Multi-Stage Cleaning CFC CFC Cu / W tertiary collimator: W

7 BLM Audit p. 6/22 Loss Rates (slow) The following table summarises the specified maximum loss rates for a safe operation of the LHC machine and its collimation system. Mode T τ R loss P loss [ s] [ h] [p/ s] [ kw] Injection cont Ramp Collision cont keep in mind that for nominal LHC operation at 7 TeV the beam lifetime is 20 h

8 BLM Audit p. 7/22 Loss Rates (fast) For an asynchronous dump (dump kicker pre-fire) it is assumed that 6 bunches can be lost into the collimation system. Similar scenario as for injection kicker failure. collimators (prim. and sec. type) can sustain shock beam impacts of 6.4 MJ mm 2 in 200 ns (7 TeV) TCT collimator may be hit by one bunch in case of misalignment of the dump protection by about 2σ, otherwise the TCT is in the shadow of the dump protection and primary/secondary collimators. The intensity of one bunch is sufficient to damage the collimator (tertiary are made of tungsten).

9 BLM Audit p. 8/22 Intensity and Cleaning Inefficiency allowed intensity beam lifetime e.g. 0.22h quench threshold p/m/s at 7 TeV p/m/s at 450 GeV dilution length 50 m (simplified) N max p τ R q L dil η c cleaning inefficiency (for L dil = 1 m) η c = 2 5 m 1 at 7 TeV η c = 1 3 m 1 at 450 GeV

10 BLM Audit p. 9/22 Simulation Tools: SixTrack For the collimation studies we use an extended version of SixTrack (full 6d treatment) including a scattering routine for simulating the interaction of the primary protons in the collimator (Colltrack routines). The field maps are generated using MADX (using official LHC optics). To reduce computing time only the beam halo, which hits the primary collimator (6σ half-gap), is considered in the simulations. A typical simulation tracks around 5 million particles over 200 turns. Reminder: aim is a cleaning inefficiency of 2 5 m 1 In general the simulation treats only the beam halo particle, beam gas interactions are not included. But it is possible load an external distribution for tracking studies (e.g. for kicker failure or for p-p interactions)

11 BLM Audit p. /22 Simulation Tools: Beam Loss Pattern The tracking information received by SixTrack is afterwards analysed using the beam loss pattern program. It compares the particle tracks with an detailed aperture model and returns the loss locations (particles touching the aperture before being absorbed in a collimator) with an cm resolution. S. Redaelli

12 BLM Audit p. 11/22 System Performance at 7TeV (Phase1) [1/m] local inefficiency η c -4-5 IR1 IR2 IR3 IR4 IR5 IR6 IR7 IR τ =.0h τ = 1.0h τ = 0.2h low β optics, 7000GeV inter action points losses in warm section losses in cold section losses in collimator beam 1 7 TeV horizontal betatron halo standard settings ideal machine s [m] [1/m] local inefficiency η c τ =.0h τ = 1.0h τ = 0.2h low β optics, 7000GeV inter action points losses in warm section losses in cold section losses in collimator s [m] beam 2 7 TeV horizontal betatron halo standard settings ideal machine

13 BLM Audit p. 12/22 Cleaning Insertion in IR7 [1/m] local inefficiency η c τ =.0h τ = 1.0h τ = 0.2h low β optics, 7000GeV inter action points losses in warm section losses in cold section losses in collimator s [m] [1/m] local inefficiency η c τ =.0h τ = 1.0h τ = 0.2h low β optics, 7000GeV inter action points losses in warm section losses in cold section losses in collimator s [m]

14 BLM Audit p. 13/22 System Performance at Injection [1/m] local inefficiency η c -4-5 IR1 IR2 IR3 IR4 IR5 IR6 IR7 IR quench level injection optics, 450GeV inter action points losses in warm section losses in cold section losses in collimator beam GeV horizontal betatron halo standard settings ideal machine s [m] [1/m] local inefficiency η c quench level injection optics, 450GeV inter action points losses in warm section losses in cold section losses in collimator s [m] beam GeV horizontal betatron halo standard settings ideal machine

15 BLM Audit p. 14/22 System Performance at 7TeV (Phase1) (with closed orbit, alignment error, jaw flatness error) η [m 1 ] η [m 1 ] IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Warm losses Cold losses Inelastic scattering on collimators Quench limit s [km] IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1 Warm losses Cold losses Inelastic scattering on collimators Quench limit s [km] beam 1 C. Bracco horizontal betatron halo collimator misalignment closed orbit horizontal betatron halo collimator misalignment closed orbit aperture misalignment

16 BLM Audit p. 15/22 p-p Interactions (DPE) dp/p Loss loactions according to momentum loss for DPE p/m/s IR5 IR4 IR s[m] s[m] Expected loss rate for DPE and SD events at peak luminosity 34 cm 2 s 1

17 BLM Audit p. 16/22 Losses for Ions G. Bellodi LHC CWG meeting Nov.2006

18 BLM Audit p. 17/22 Simulation Results available Overview of available simulated cases. standard optics (injection, early collision, all IRs squeezed, IR1 and IR5 squeezed), ideal machine start-up configuration (early collision optics with reduced number of TCS collimators in IR7) commissioning scenarios energy ramp error scenarios collimator misalignment (tilt, gap, offset) closed orbit aperture misalignment losses from p-p interactions in the IRs (only IR5 so far)

19 BLM Audit p. 18/22 Loss Locations injection energy collision energy beam 1 beam 2 beam 1 beam 2 Q11.R3 Q27.R7 Q28.R3 MB20.L6 Q31.L7 MB11.L7 Q6L3 Q21.R7 Q11.R6 Q9.L7 DFBA.R6 Q31.R7 Q18.L4 MB16.L6 Q27.L7 MB9.L7 Q8.R7 MB34.L8 MB12.R6 MB9.L7 MB9.R7 Q33.L8 Q.L4 MB14.L6 Q23.L7 Q8.L7 MB9.R7 Q33.L8 Q25.R6 Q8.L7 MB11.R7 Q29.L8 Q22.R5 MB12.L6 Q19.L7 MB8.L7 Q9.R7 Q25.L8 Q33.R6 MB8.L7 Q11.R7 Q25.L8 Q28.L6 MB9.L6 MB19.L7 Q.R7 Q17.L8 Q19.L7 MB13.R7 Q2.R8 MB28.L6 MB8.L6 Q15.L7 MB11.R7 Q16.R8 Q13.L7 Q13.R7 Q6.R8 Q25.L6 Q4.L6 MB15.L7 Q11.R7 Q30.R8 MB13.L7 Q23.R7 Q20.L6 Q11.R6 Q11.L7 Q13.R7 Q22.L1 Q11.L7 MB21.R7 MB11.L7 (see thesis G. Robert-Demolaize) p-p interactions for beam 2 from IR5 MB.A9L5 MB.B9L5 Q9.L5 MB.B11L5 MS.11L5 Q11.L5 MB.C13L5 MS.13L5 Q13.L5 MS.21L5 Q21.L5 MS.24L4 Q24.L4 MS.22R3 Q22.R3 MS.14R3 Q14.R3 BPM.6R3

20 BLM Audit p. 19/22 Summary Full set of simulation tool available to simulate the cleaning inefficiency of the collimation system and generate beam loss maps along the ring. Loss location for different optics, running scenarios and mechanical alignment errors available. Standard run considers around 5 million particles, due to the required low cleaning inefficiency only a few hundred particles are lost to the aperture. Main loss locations (see also previous slide): dispersion suppressor after the cleaning insertions dispersion suppressor in experimental insertion (for p-p interaction) Q6 in IR3

21 BLM Audit p. 20/22 Spare Slides

22 BLM Audit p. 21/22 Estimated Damage Interlock Limits R. Assmann: Damage Limits for LHC Collimators (note in preparation)

23 BLM Audit p. 22/22 Estimated Damage Interlock Limits R. Assmann Damage Limits for LHC Collimators (note in preparation)